Tyrella Fascia.
Tyrrell's fascia (fascia tyrrelli; f. tyrrell) is a deep layer of the cervical fascia located between the transverse processes of the C7 and Th1 vertebrae. It inserts on the transverse process of C7 and extends cranial to the occipital bone.
Tyrrell's fascia divides the posterior cervical region into two parts: the anterior, containing the long neck muscles, and the posterior, where the short neck muscles are located. This fascia provides separate sliding of the anterior and posterior muscles during neck movements.